1. Field of the Invention
The present invention relates to a method for manufacturing a silicon carbide fiber reinforced glass composite which consists of silicon carbide fibers having glass melt or glass matrix permeated therebetween to such extent as not to leave any cavities and which is characterized by light weight and other various excellent properties such as superior flexibility, strength, oxidation stability and heat resistance.
2. Prior Art
Conventionally, as heat-resisting structural materials capable of withstanding heat at 800.degree. C. or more, Ni-, Co-, W-, Fe- and Cr-based heat-resisting alloys and titanium-based alloys have been used. When exposed to such high temperatures, however, the strengths of such metallic materials are known to decrease to less than 50%, very often 10-20%, of those at room temperature, so that they can only narrowly withstand such high temperatures.
The alloys such as Fe, Ni and Co alloys have such relatively large specific gravities ranging from 7 to 9 that they are disadvantageous for use as materials for the manufacture of aircrafts requiring their weight to be as light as possible, and these disadvantages have been a bar to further improvements in the performances of various aircrafts. Furthermore, metallic materials such as titanium occur in a limited quantity among natural resources, thereby raising them in price.
Thus, in the field of heat-resisting structural materials, researchers and developments of high strength fiber reinforced composites such as high strength fiber reinforced ceramic composites, high strength fiber reinforced resin composites and high strength fiber reinforced metal matrix composites and ceramic materials have been intensively made in recent years, and these composites and materials are expected to find a wide use as the materials for aircrafts, rockets, spacecrafts and so forth.
Among the fiber reinforced metal matrix composites, a fiber reinforced aluminum alloy composite capable of withstanding a relatively low temperature of 400.degree. C. is known as the most common composite at present. On the other hand, the ceramic materials such as silicon carbide, silicon nitride, alumina and zirconia are capable of maintaining their original strength even at 800.degree. C. or more, but they are not able to be put to practical use because of their inherent brittleness which has not been solved yet. Under such circumstances, a fiber reinforced glass composite, one of the fiber reinforced ceramic composites, is coming to the fore as the most promising high heat-resisting material because of its advantageous properties such as high strength and high toughness at high temperatures and light weight.
As reinforcing fibers for the fiber reinforced glass composite, there are graphite fibers, alumina fibers and silicon carbide fibers, but one of the most important problems common to them is the maximum working temperature. The upper limit of working temperature is comparatively high in, for example, graphite fiber reinforced glass composites or alumina fiber reinforced glass composites, but such working temperatures are still not high enough to meet the requirements for actual higher heat resistance. For example, the graphite fiber reinforced glass composites have high levels of strength, fatigue resistance and rupture resistance but they are disadvantageously subject to harmful oxidation of fibers at temperatures higher than 400.degree. C. On the other hand, the alumina fiber reinforced glass composites are stable against such oxidation at high temperatures, but they raise problems concerning its strength and rupture resistance since the alumina fibers react with the glass to cause vitrification, thus causing the erosion of reinforcing fibers and the deterioration of the strength and rupture resistance of the composites.
In the case of the silicon carbide fiber reinforced glass composite, however, the silicon carbide fibers themselves are resistant to oxygen in air at a high temperature, able to maintain their excellent strength and do not react with the glass, and thus the glass composite reinforced by the silicon carbide fibers has higher strength, toughness and oxidation resistance. The silicon carbide fibers discussed herein are those with diameters of not more than 50.mu. manufactured from an organic silicon compound.
Thus, the silicon carbide fiber reinforced glass composite has come to the fore recently because of its high heat resistance, oxidation resistance, strength and rupture resistance. Conventionally, silicon carbide fiber reinforced glass composite is manufactured from a preform sheet manufactured by a powder slurry method. In the powder slurry method, the glass powder is made to adhere to the silicon carbide fibers through a resin such as polyvinyl alcohol, but the resulting composite is known to have the disadvantage that the permeation of the glass powder among the fibers is not sufficient thereby causing insufficient adhesion between the silicon carbide fibers and the glass. Besides, this method requires the resin and other chemicals used to be removed by heat treatment prior to the molding process, but such heat treatment is not so complete that the trace of carbon is left on the surfaces of the fibers thereby causing the deterioration of the properties of the resulting composite.